Hey, welcome to the forums (though I'm new enough myself that "welcoming" anyone seems out of place). In any case, I asked about this earlier today;
here's a link with the replies. General consensus seems to be that it's positional, but you generally want to be limping/playing for set value in larger pots with worse position and lower pairs. Given higher pairs, better position and fewer people in the pot, they can be played a bit more strongly. The link has examples. Hope that helps,
Blue